Is it true that the Earth's magnetosphere is expanding?

Although the shape of the Earth's magnetosphere changes depending on the
strength of the solar wind, I have not heard that there is an overall
expansion to this field over millions of years.
In fact, because the magnetic field of the
Earth increases and decreases with roughly a 250,000 year period, it does
undergo expansion and contraction every 1/4 million years. Currently, the
strength of the field is decreasing so that the magnetosphere is
also decreasing in strength and in size.